Stiffness Modulus Asphalt Mixture and Its Enhanced Resonance in Nondestructive Testing
Enhanced resonance search (ERS) is a nondestructive testing technique that utilizes a unique tool called the pavement integrity scanner to assess the condition of a pavement (PiScanner). In this article, we are going to the stiffness modulus of the asphalt mixture.
asphalt mixture components
Using the theory of surface wave and body wave propagation, this method can be used to measure the thickness of the road pavement structure and the profile of shear wave velocity.
In this study, the dynamic elastic modulus of the asphalt pavement surface layer was determined using shear wave velocities, while the actual thickness of the asphalt pavement surface layer was measured using the ERS technique.
asphalt mix base course
The results were then compared to the requirements of the Malaysian PWD, MDD UKM, and IKRAM for a total of fifteen locations.
The elastic modulus of materials was discovered to range from 3929 MPa to 17726 MPa. A difference of 20 to 60% could be seen when comparing the average sample thickness to the design thickness of MDD UKM.
The thickness of the asphalt surface layer complied with Malaysian PWD and MDD UKM specifications, but some stiffness measurements were higher than expected.
In order to provide a road surface with enough skid resistance and function to dissipate vehicle load to the subgrade, flexible pavement is a composite material made of a combination of aggregate, sand, bitumen, and filler material.
At the same time, the flexible pavement has a long life expectancy without the need for frequent maintenance.
To ensure that it can function properly, pavement is designed with respect to four key factors: thickness, strength, resistance to surface water, and surface texture.
The goals of pavement design typically involve choosing the right building materials and making sure that each layer's thickness is appropriate so that the flexible pavement layer can shield the subgrade from the effects of the traffic load.
However, flexible pavement quality degrades over time and is influenced by the caliber of the materials used, the environment, and the amount of traffic.
The lifespan of flexible pavement will be shortened by reduced thickness due to increased traffic on aging road infrastructure.
To prevent damage to the pavement brought on by the environment and traffic volume, it is important to emphasize the precise thickness of each layer.
An evaluation of the present stiffness and the anticipated pavement strength in the future are the main factors that need to be taken into account in road pavement management systems.
The elastic modulus parameter, which is important in forecasting and assessing the performance of flexible pavement when static and repetitive traffic loads are applied, can be used to determine the strength of the flexible pavement.
Falling weight deflectometer (FWDs) are typically used as a tool or pieces of equipment to measure the stiffness of the paving system. The FWD is a nondestructive test (NDT) experiment that applies an impulse load to the pavement surface through a circular steel plate.
asphalt mixture ratio
Maximum dynamic displacements are used to gauge how stiff the pavement layers are. The FWD data includes information on the environment, layer thickness, material response functions, and traffic load.
Due to its simplicity of use and effective outcomes, this testing tool is widely used. Ground penetrating radar (GPR) is another instrument that can be used to gauge the thickness of pavement.
A survey vehicle was used to position an antenna that picked up brief pulses of electromagnetic energy from the pavement in order to record the pavement layer systems.
A radar waveform made up of a series of pulses will contain information about the characteristics and thickness of the pavement layer system. This method of evaluating the pavement layer system is precise and non-destructive.
A new device called a pavement integrity scanner (PiScanner) was recently created by Joh et al. to evaluate the stiffness of pavement layers systems while also determining the pavement's thickness.
In this study, the thickness and stiffness of the asphalt surface layer were measured using PiScanner and the enhanced resonance search (ERS) method.
The PiScanner, which uses the ERS method, has already been tested on rigid pavement structures, but its suitability for flexible pavement hasn't been looked into.
Therefore, the purpose of this study is to determine whether the PiScanner can accurately measure the thickness of an existing pavement system on the flexible pavement.
On the basis of the elasticity theory, the stiffness of the flexible pavement will also be determined.
However, the asphalt surface layer, which is made up of the wearing and binder courses, will be the sole focus of the evaluation of flexible pavement structure.
The ERS method was used to calculate the thickness of the asphalt layer. This technique combines the SASW and resonance methods, in which the SASW determines the shear wave velocity profile and the resonance search determines the thickness of the asphalt.
The pavement layer is subjected to a resonance search to ensure that the pavement layer thickness is accurately measured due to the limitations of measuring the pavement layer thickness by SASW.
asphalt mixture volumetrics
Surface wave velocity is used to calculate the elastic properties of the material in SASW, which is then used to assess the strength of the concrete structure and pavement system.
By fully utilizing the benefits of surface waves, this method is also capable of determining the elastic modulus and thickness of a layered system.
Because conventional computation requires 15 to 30 minutes to compute theoretical modeling of wave propagation, Joh et al. created an automation algorithm that was used to simplify vertical profiling of concrete modulus in the rigid pavement.
This algorithm reduced the analysis time to between three and five minutes.
This automation algorithm was applied to the phase velocity calculation and resonance search processes. The fundamental wave group is taken from the surface wave that is propagating for automated phase velocity calculation.
A Gabor spectrum's wave group will be looked at for the extraction.
While automated resonance search used the iterative comparison of field measurements and theoretical model results to find accurate thickness, theoretical modeling was used to define a resonant frequency from the frequency response curve.
Numerous benefits come from choosing the frequency domain and wave number of the R wave transform analysis over the time domain, including how simple it is to solve the wave propagation equation in the available frequency domain and perform frequency and wave number analysis.
This is due to the fact that time domain numerical integration analysis is more challenging.
By analyzing frequency and wave number, it is possible to learn everything there is to know about wave propagation. Nolet and Panza demonstrate through frequency and wave number analysis how convincing the production of a spectrum is.
Additionally, a technique known as the fast Fourier transform that uses the Fourier transform to analyze the spectrum using numerical methods that can be calculated digitally has been developed (FFT). The frequency domain can be used to measure and analyze dynamic systems.
Body wave measurement is a resonance-based technique based on different types of reflection in bounded media. Finding the dominant frequency of multiple wave reflections using this method is reliable.
The impact echo (IE) technique is one resonance technique. IE entails making a quick impact on the structure's surface in order to generate low-frequency waves.
If there is a flaw inside the structure or on the external borders, the generated wave will propagate into the structure before being reflected.
Stiffness Modulus
The maximum shear modulus or stiffness of a material under 0.0003% of strain can be calculated using the wave propagation theory from the velocity of the S wave or shear wave.
The PiScan Probe is made up of a sensor unit that propagates sensor waves using an accelerometer and an instrumented hammer that serves as an impulse generator. Two accelerometers are included in this apparatus.
There is a weight on each of the two accelerometers, and the distance between them has been set to 0.15 and 0.30 m.
The purpose of this weighting is to guarantee perfect contact between the accelerometer and the pavement. As a result, any interference and the detector's time interval can be removed.
Although the accelerometer in the PiScan Probe has a unique frame, Joh et al. explain that the measured signal is almost identical to the signal measured by the bare accelerometer.
The accelerometers' detection of a wave signal in the form of amplitude and wave propagation time will be recorded. A PiScan Analyzer, which performs as a data analyst and is outfitted with dynamic signal analysis (DSA) or FFT analysis, is a component of POLCCA.
The analyzer carries out the ERS measurement and examines data collected automatically. A coupling AC/DC, four analog channels, anti-masking filters, and an analog trigger are also included.
The SASW and resonance methods are combined to create the ERS method. There are thus two configurations for the impulse generator and accelerometers.
An instrumented hammer and two accelerometers are used to measure the wave signal in surface wave measurements or SASW. The distance between MP1 and MP2 is 0.30 m, and the instrumented hammer's distance from MP1 is the same as that distance.
The maximum depth is indicated by the distance between the instrumented hammer and MP1. The instrumented hammer and accelerometer used in the resonance method are placed 0.075 m apart from MP1.
The study's main focus was the design of the flexible pavement on the main campus of UKM in Bangi, Selangor.
The first loop and the second loop, can be used to divide the study area into two sections. Seven locations in the second loop and a total of eight locations in the first loop were chosen for measurement.
The ERS combines two techniques when analyzing field data. As a result, there are two main phases to the data analysis in this method. Using SASW, the shear wave velocity profile is calculated in the first stage; the asphalt layer thickness is calculated in the second stage.
Prior to body wave analysis, surface wave analysis is completed to create a graph of shear wave velocity versus depth, which will allow for a more precise assessment of the thickness of the asphalt layer.
hot asphalt mix near me
Seismic data acquisition is divided into four main steps. The placement of the accelerometer and impulse generator to create waves is the first. The PiScanner Analyser must be configured for the measurement in the second step.
The resonant body wave and the surface wave are measured in the third and fourth steps, respectively.
Two accelerometers are first set up on the pavement surface for the ERS measurement. To guarantee that the data obtained are satisfactory, the accelerometers should be in contact with the pavement surface and free of any holes.
The pavement is then temporarily altered at two locations, 300 mm and 75 mm from the first accelerometer, using the hammer. Choosing the PiScanner Analyser's settings is the second step.
The hammer is set at 75 mm away from the first accelerometer in the third step, which entails gathering data from body wave resonance signals.
The average of the signal produced by ten hammer blows is recorded. Recording the surface wave is the last step in the acquisition of seismic data.
Ten hammer blows are delivered with a 300 mm distance between the impact source and the first receiver, and the average of the resulting signal is recorded.
From the study, the following conclusions can be made.
The elastic modulus range of the asphalt pavement materials found in this study, which ranges from 3929 MPa to 17726 MPa, is greater than the range established by the IKRAM Group Sdn. Bhd.
Some of the measured elastic values, however, are recorded within the Malaysian PWD standard. This occurred as a result of the different material quality at each location due to the time the pavement was built.
According to the ERS method, the surface layer of asphalt has an average thickness of 0.04 to 0.08 m. This still falls within the 0.04 to 0.14 m range of Malaysian PWD standards.
Furthermore, the discrepancy between the asphalt surface layer thickness determined by this study and the design thickness recommended by the MDD UKM does not exceed 60%.
The research demonstrates that the stiffness and thickness of the asphalt surface layer can be measured using the ERS method and the PiScanner in accordance with the established standards.
Therefore, it can be inferred that this method can also be used to gauge the thickness and stiffness of flexible pavements in addition to rigid pavements.
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